Mitsubishi Heavy Industries SCM71ZM-S1 Technical Manual page 221

Cooling
Heat exchanger
sensor
Heating
Cooling
Ourdoor air
temperature sensor
Heating
Discharge pipe
All modes
sensor
(9) Checking the indoor electrical equipment
(a) Indoor PCB check procedure
Is there voltage between terminal
blocks ① and ② ? (AC 220/230/240
V)
YES
Is the fuse burnt out? (3.15 A)
YES
Is the voltage between terminal
blocks ② and ③ oscillating between
DC 0 and 20V?
YES
Indoor electrical components
are normal.
(b) Indoor unit fan motor check procedure
(i) Indoor PCB output check
1)
2)
3)
DC several V
(4 – 6 V)
CNU
(ii) Fan motor resistance check
Measuring point
① − ③
−
④ − ③
NO
Inspect power source
for outdoor unit.
NO
Replace fuse.
NO
Replace indoor PCB.
(–)
GND
DC15V
⑥ ⑤ ④ ③
⑥ ⑤ ④ ③
FM
i
Resistance when normal
−
k
Defrosting is performed for 10 minutes at approx. 40 minutes.
Defrosting is performed for 10 minutes at approx. 40 minutes.
DC 280V
Indoor PCB
② ①
② ①
220
- -
'17 • SCM-T-225
① ④ ⑤
Measuring Resistance when
point normal
① − ③
④ − ③
⑤ − ③